Negative Tone Developer Compatible Photoresist Composition and Methods of Use

ABSTRACT

Compositions and methods herein include negative tone developer compatible photoresist compositions and methods of using such compositions. This includes a positive tone photoresist that can be developed using negative tone developers in that unexposed portions of the positive tone photoresist are dissolvable by one or more negative tone developer solvents. One embodiment includes a negative tone developer compatible photoresist with little or no etch resistance. Non-resistive photoresist materials as described herein can include one or more radiation-sensitive attributes (for example, the photoresist can be patterned, de-protected, solubility shifted, interact with photo chemistries, and respond to exposure doses), except that these materials have effectively no etch resistance. Such compositions can be effectively free from components, functional groups, or additives that provide or increase etch resistivity to a wet or dry etch process.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication No. 62/021,756, filed on Jul. 8, 2014, entitled “NegativeTone Developer Compatible Photoresist Composition and Methods of Use,”which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Techniques disclosed herein relate to microfabrication, and relate inparticular to photolithography.

In material processing methodologies (such as photolithography),creating patterned layers typically involves the application of a thinlayer of radiation-sensitive material, such as photoresist, to a surfaceof a substrate. This radiation-sensitive material is transformed into apatterned mask that can be used to etch or transfer a pattern into anunderlying layer on a substrate. Patterning of the radiation-sensitivematerial generally involves exposure by a radiation source through areticle (and associated optics) onto the radiation-sensitive materialusing, for example, a photolithographic system. This exposure creates alatent pattern within the radiation-sensitive material which can then bedeveloped. Developing refers to dissolving and removing a portion of theradiation-sensitive material to yield a topographic or physical pattern.For example, developing can include removal of irradiated regions of theradiation-sensitive material (as in the case of positive photoresist),or non-irradiated regions (as in the case of negative resist) using adeveloping solvent. The topographic pattern can then function as a masklayer for subsequent processing.

SUMMARY

“Resist” compositions and films, as used in the microfabricationindustry, generally refer to materials that resist an etch process. Thisincludes resistance to wet etch processes, and also to plasma-based dryetch processes. Such films are commonly described as photoresistsbecause of their ability to have a solubility shift in response toexposure to a particular radiation wavelength or wavelengths.

Current photolithography trends include using negative tone developercompatible photoresists. Such photoresists are positive tonephotoresists but are developed using a negative tone developmenttechnique. A conventional positive tone photoresist responds to actinicradiation by de-protecting exposed regions to a developing solvent. Inother words, portions of a positive tone photoresist exposed toradiation have a solubility shift in which solubility is increased to apositive tone developer. With negative tone development, however, apositive photo resist is used, but it is the unexposed (protectedregion) that is dissolved by negative tone developer solvents. There areadvantages to using negative tone development schemes. Neverthelessrelief patterns and lines created using a negative tone developmentscheme can have an undesirable line edge or line width roughness. Thisroughness can then limit subsequent pattern transfer andmicrofabrication processes.

Techniques disclosed herein include negative tone developer compatiblecompositions and methods of using such compositions. This includes apositive tone photoresist that can be developed using negative tonedevelopers in that unexposed portions of the positive tone photoresistare dissolvable by one or more negative tone developer solvents. Oneembodiment includes a negative tone developer compatible photoresistwith little or no etch resistance. In other words, compositions caninclude a non-resistive photoresist that is compatible with negativetone development. Non-resistive photoresist materials as describedherein include one or more radiation-sensitive attributes (for example,the photoresist can be patterned, de-protected, solubility shifted,interact with photo chemistries, and respond to exposure doses), exceptthat these materials have effectively no etch resistance. In the contextof microfabrication, such a composition runs counter to conventional andhistorical photolithography practices because the purpose of a resist isto provide a patterned mask that can be used to transfer a pattern intoan underlying layer by etching the underlying layer. For example, if arelief pattern using such a non-resistive photoresist was subjected to agiven etch process immediately after developing the relief pattern, thenthe relief pattern will be quickly etched away or etched away prior toetch transfer of the relief pattern into an underlying layer.Nevertheless, such a non-resistive positive tone photoresist that iscompatible with negative tone development is beneficial, and isparticularly beneficial to microfabrication processes.

Compositions described herein can be used with methods described hereinthat include one or more post-development techniques. Techniques hereincan include various types of image reversal techniques in which a givenrelief pattern is reversed prior to etch transfer. Techniques herein canalso include various types of photoresist strengthening techniques thatcreate etch resistivity after photoresist development.

Negative tone developer compatible photoresists having substantially noetch resistivity, as disclosed herein, provide various benefits.Positive tone photoresists that are negative tone developer compatibleconventionally include one or more components that provide or promoteetch resistivity. For example, such additives can include cage groups,adamantyl groups, lactone groups, or other additives that provides etchresistance. By removing these etch resistive components, a morecost-efficient photoresist can be generated. Moreover, these resistivecomponents typically add bulk to a given photoresist and can beresponsible for increasing edge or surface roughness. Withoutetch-resistive groups included, a given positive tone photoresist canhave a roughness reduction of up to one nanometer or more.

Of course, the order of discussion of the different steps as describedherein has been presented for clarity sake. In general, these steps canbe performed in any suitable order. Additionally, although each of thedifferent features, techniques, configurations, etc. herein may bediscussed in different places of this disclosure, it is intended thateach of the concepts can be executed independently of each other or incombination with each other. Accordingly, the present invention can beembodied and viewed in many different ways.

Note that this summary section does not specify every embodiment and/orincrementally novel aspect of the present disclosure or claimedinvention. Instead, this summary only provides a preliminary discussionof different embodiments and corresponding points of novelty overconventional techniques. For additional details and/or possibleperspectives of the invention and embodiments, the reader is directed tothe Detailed Description section and corresponding figures of thepresent disclosure as further discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of various embodiments of the invention andmany of the attendant advantages thereof will become readily apparentwith reference to the following detailed description considered inconjunction with the accompanying drawings. The drawings are notnecessarily to scale, with emphasis instead being placed uponillustrating the features, principles and concepts.

FIGS. 1A-1E are cross-sectional schematic views of an example substratesegment showing a process flow according to embodiments disclosedherein.

FIGS. 2A-2F are cross-sectional schematic views of an example substratesegment showing a process flow according to embodiments disclosedherein.

FIGS. 3A-3E are cross-sectional schematic views of an example substratesegment showing a process flow according to embodiments disclosedherein.

FIGS. 4A-4F are cross-sectional schematic views of an example substratesegment showing a process flow according to embodiments disclosedherein.

FIGS. 5A-5H and 5J are cross-sectional schematic views of an examplesubstrate segment showing a process flow according to embodimentsdisclosed herein.

FIGS. 6A-6G are cross-sectional schematic views of an example substratesegment showing a process flow according to embodiments disclosedherein.

DETAILED DESCRIPTION

Techniques disclosed herein include negative tone developer compatiblecompositions and methods of using such compositions. This includes apositive tone photoresist that can be developed using negative tonedevelopers in that unexposed portions of the positive tone photoresistare dissolvable by one or more negative tone developer solvents. Oneembodiment includes a negative tone developer compatible photoresistwith little or no etch resistance. In other words, compositions caninclude a non-resistive photoresist that is compatible with negativetone development. Non-resistive photoresist materials as describedherein include one or more radiation-sensitive attributes (for example,the photoresist can be patterned, de-protected, solubility shifted,interact with photo chemistries, and respond to exposure doses), exceptthat these materials have effectively no etch resistance.

One example embodiment includes a positive tone photoresist that isnegative tone developer compatible, and that is substantially oreffectively free from components, functional groups, or additives thatprovide or increase etch resistivity to a wet or dry etch process. Apositive tone photoresist is a photoresist that, in response to exposureto radiation, increases its solubility to one or more positive tonedevelopers. In other words, regions that are exposed to light becomede-protected to a positive tone developer such that a positive tonedeveloper can dissolve exposed portions. A negative tone developer is adeveloper chemistry that dissolves un-exposed portions of a givenpositive tone photoresist film. Thus, as used herein, a negative tonedeveloper compatible photoresist is a positive tone photoresist that isformulated to have a solubility shift in response to exposure to actinicradiation (usually at a particular light wavelength) such that exposedportions become insoluble to a negative tone developer and un-exposedportions remain soluble to a negative tone developer. The exposedportions can become soluble to a positive tone developer chemistry.

Positive tone developer chemistries have been conventionally used.Developing a pattern using positive tone development (PTD) involvesremoving an exposed region of a latent pattern in a photoresist film bythe action of an aqueous base developer such as aqueoustetramethylammonium hydroxide (TMAH). An exemplary positive tonedeveloper is 0.26 N TMAH (aq.). Alternatively, the same latent patternin the photoresist film can be developed using an organic solventdeveloper to provide negative tone development (NTD) in which theunexposed region of the latent pattern is removed by the action of anegative tone developer. Useful solvents for negative tone developmentinclude those also useful for dissolving, dispensing, and coating.Exemplary negative tone developer solvents include methyl2-hydroxybutyrate (HBM), propylene glycol monomethyl ether acetate(PGMEA), methoxyethoxypropionate, ethoxyethoxypropionate, andgamma-butyrolactone, cyclohexanone, 2-heptanone, and a combinationcomprising at least one of the foregoing solvents.

Another embodiment can include a positive tone photoresist compositioncomprising a polymer component. A resin component can be included, andthis resin component can be selected to exhibit increased alkalisolubility under action of acid. An acid generator component can beincluded that generates acid in response to exposure to actinicradiation (photo acid generator). The composition can also include anorganic solvent. The organic solvent can facilitate dispensing and spincasting onto a substrate. The organic solvent can be baked out to helpcreate a functional layer of photoresist. The positive tone photoresistcomposition is substantially free (or entirely free) from functionalgroups that increase etch resistivity.

Another embodiment can include a photoresist composition comprising oneor more polymer components, one or more resin components, one or morephoto acid generator compounds that generate photo acid in response toexposure to a predetermined wavelength of light, and one or moresolubility-changing groups that react to generated photo acid by makingpolymer components insoluble to a negative tone developer. Thisphotoresist composition has approximately no etch resistivity to dry orwet etch processes.

Another embodiment includes a photoresist composition comprising one ormore resin components that exhibit a change in solubility under actionof acid, one or more photo acid generator compounds that generate photoacid in response to exposure to radiation, and one or more solubilitychanging groups that react to generated photo acid by making the polymercomponents insoluble to a negative tone developer. This photoresistcomposition has approximately no etch resistivity to dry or wet etchprocesses such as plasma-based etching chemistries.

One embodiment includes a photoresist composition comprising a positivetone resist polymer component, a resin component, an acid generatorcomponent that generates acid in response to exposure to actinicradiation, a solvent, and a solubility-shifting component that causesregions of the photoresist composition exposed to actinic radiation tobecome soluble to a positive tone developer. This composition isformulated such that regions unexposed to actinic radiation remainsoluble to a negative tone developer. This photoresist composition isalso formulated such that an amount of functional groups, included inthe photoresist composition, that increase etch resistance, to a wetetch or dry etch process, ranges from 0.0% to 15% by weight based on atotal weight of solid content in the photoresist composition. Thus,there can either be no such functional groups included in thecomposition, or an amount too small to provide any effective etchresistance. In other embodiments such etch-resistance promotingfunctional groups are less than 10% or less than 5% by weight based on atotal weight of solid content. In other words, an amount ofetch-resistance promoting additives or components is sufficiently low toprovide substantially no etch-resistance, especially as compared toetch-resistance of target layer to be etched.

Another embodiment is a photoresist composition that includes aphotoresist polymer component, a resin component, an acid generatorcomponent that generates acid in response to exposure to actinicradiation, a solvent, and a solubility shifting component that causesregions of the photoresist composition exposed to actinic radiation tobecome soluble to a positive tone developer, wherein regions unexposedto actinic radiation remain soluble to a negative tone developer. Anamount of functional groups, included in the photoresist polymercomponent that increase etch resistance to a wet etch or dry etchprocess, ranges from 0.0% to 15% by weight based on a total weight ofthe photoresist polymer component. In other embodiments the amount offunctional groups, included in the photoresist polymer component thatincrease etch resistance to a wet etch or dry etch process, is less than10% or 5%.

One embodiment includes a photoresist composition comprising a positivetone resist polymer component, a resin component, an acid generatorcomponent that generates acid in response to exposure to actinicradiation, a solvent, and a solubility-shifting component that causesregions of the photoresist composition exposed to actinic radiation tobecome soluble to a positive tone developer. This composition isformulated such that regions unexposed to actinic radiation remainsoluble to a negative tone developer. This photoresist composition isformulated such that the photoresist composition (or film made from thephotoresist composition) has an Ohnishi parameter value greater thanapproximately 3.0. In other embodiments the Ohnishi parameter value canbe greater than 4.0 or even 2.7.

Another embodiment includes a photoresist composition comprising apolymer that includes a structural unit, a radiation-sensitive acidgenerator that generates acid upon exposure to light, an acid-labilegroup that shifts solubility of the polymer in response to presence ofacid, the polymer being compatible with a negative tone developer suchthat unexposed regions of the polymer are soluble in the presence of anegative tone developer. The acid-labile groups are selected to causeexposed regions of the polymer to become insoluble to a negative tonedeveloper. This photoresist composition has an Ohnishi parameter valuegreater than approximately 3.0.

Another embodiment includes a photoresist composition comprising apositive tone photoresist component that is soluble to an organicsolvent. The positive tone photoresist component can include a polymerand/or resin. The photoresist also comprises a radiation-sensitive acidgenerator that generates photo acid in response to exposure to apredetermined wavelength of light, and a solubility-shifting componentthat, in response to the presence of photo acid, causes the positivetone photoresist component to become insoluble to an organic solventdeveloper, wherein the photoresist composition is formulated such that,when formed into a layer of photoresist, the layer of photoresist has anOhnishi parameter greater than 3.0. In other embodiments, the positivetone photoresist component comprises a polymer or a resin and polymer

The so-called Ohnishi parameter is a measure of a given material's etchresistance. Wet or dry etching resistance can be estimated by theOhnishi parameter of a resist composition. The Ohnishi parameter can bedefined as: (N/(Nc-No)), where N expresses the total number of atoms, Ncexpresses the number of carbon atoms, and No expresses the number ofoxygen atoms. Thus, a photoresist with high carbon content acts as abetter etch mask than does a photoresist with high oxygen content underoxygen plasma reactive ion etching (RIE). Excellent dry etching abilityis obtained when the Ohnishi parameter is small. For example, a resistcomposition having an Ohnishi parameter that is equal to or less than4.0 has good etch resistance, with values less than 2.5 highly desirablefor etch resistance. For example, a high carbon content polymer, such aspoly(hydroxy-styrene), has an Ohnishi parameter (etch rate) of about2.5, while an oxygen-containing polymer such as poly(methylmethacrylate)has an Ohnishi parameter of about 5.0. Any ring structures present canalso contribute to a high etch resistance. Thus, materials with anOhnishi parameter of about 3.0 and greater have little or no etchresistance.

Another example embodiment includes a photoresist composition thatincludes a photoresist polymer component, a resin component, an acidgenerator component that generates acid in response to exposure toactinic radiation, a solvent, and a solubility-shifting component thatcauses regions of the photoresist composition exposed to actinicradiation to become soluble to a positive tone developer, and such thatregions unexposed to actinic radiation remain soluble to a negative tonedeveloper. This photoresist composition, when deposited on a substrateas a photoresist film, provides an etch resistivity such that a givenplasma-based etching process etches the photoresist film at a greateretch rate than the given plasma-based etching process etches a materialselected from the group consisting of silicon dioxide, silicon,polycrystalline silicon, silicon nitride, tetraethyl orthosilicate,amorphous carbon, and silicon oxynitride. This photoresist film can havean etch resistivity less than other materials conventionally patternedusing photoresist masks.

Another embodiment includes a positive tone photoresist compositioncomprising a positive tone resist polymer component, a resin component,an acid generator component that generates acid in response to exposureto actinic radiation, a solvent, and a solubility-shifting componentthat causes regions of the positive tone photoresist composition exposedto actinic radiation to become soluble to a positive tone developer.This composition is formulated such that regions unexposed to actinicradiation remain soluble to a negative tone developer. This positivetone photoresist composition is free or substantially free fromfunctional groups that increase etch resistance to a wet or dry etchprocess.

Another embodiment includes a photoresist composition comprising one ormore polymer components, one or more resin components, one or more photoacid generator compounds that generate photo acid in response toexposure to a predetermined wavelength of light, and one or moresolubility changing groups that react to generated photo acid by makingthe polymer components insoluble to a negative tone developer, whereinthe photoresist composition has substantially no etch resistivity to dryor wet etch processes. One embodiment includes a photoresist compositionthat includes a negative tone developer compatible photoresist that issubstantially free from functional groups that increase etch resistivityto a wet or dry etch process.

One embodiment includes a photoresist composition comprising one or moreresin components that exhibit a change in solubility under action ofacid, one or more photo acid generator compounds that generate photoacid in response to exposure to a radiation, and one or more solubilitychanging groups that react to generated photo acid by making the polymercomponents insoluble to a negative tone developer. This photoresistcomposition has substantially no etch resistivity to dry or wet etchprocesses. Other embodiments include a photoresist composition thatcomprises a positive tone photoresist component that is soluble to anorganic solvent, a radiation-sensitive acid generator that generatesphoto acid in response to exposure to a predetermined wavelength oflight, a solubility-shifting component that, in response to the presenceof photo acid, causes the positive tone photoresist component to becomeinsoluble to an organic solvent developer, and that is substantiallyfree of cage groups, adamantyl groups, lactone groups, ligand groups, orother additives primarily designed (or that primarily function) topromote etch resistance.

Another embodiment includes a positive tone photoresist compositioncomprising a polymer component, a resin component that exhibitsincreased alkali solubility under action of acid, an acid generatorcomponent that generates acid in response to exposure to actinicradiation, and an organic solvent. The positive tone photoresistcomposition is substantially free from functional groups that increaseetch resistivity. Another photoresist composition comprises (a) apolymer, (b) a resin, (c) de-protection group, (d) a solvent, and (e) aphotoacid generator, wherein the photoacid generator generates acid uponexposure to radiation, wherein the de-protection group responds to acidpresence by changing solubility of the polymer so that the polymer isinsoluble to negative tone develop solvents, and wherein the photoresistis substantially free from constituents that provide etch resistance toan etching process. Another photoresist composition comprises a positivetone photoresist with the positive tone photoresist being soluble to anegative tone developer. The negative tone photoresist is formulatedsuch that exposure to lithographic radiation causes exposed portions(through a photomask) of the positive tone photoresist to becomeinsoluble to a negative tone developer. This positive tone photoresistis free from components that provide etch resistance to a wet etchprocess or to a dry etch process.

Another embodiment can include a photoresist composition comprising oneor more polymer components, one or more resin components, one or morephoto acid generator compounds that generate photo acid in response toexposure to a predetermined wavelength of light, and one or moresolubility-changing groups that react to generate photo acid by makingpolymer components insoluble to a negative tone developer. Thisphotoresist composition has approximately no etch resistivity to dry orwet etch processes.

Another embodiment includes a photoresist composition comprising one ormore resin components that exhibit a change in solubility under actionof acid, one or more photo acid generator compounds that generate photoacid in response to exposure to radiation, and one or more solubilitychanging groups that react to generate photo acid by making the polymercomponents insoluble to a negative tone developer. This photoresistcomposition has approximately no etch resistivity to dry or wet etchprocesses.

Note that the above compositions can be formulated as a fluid that isspin castable such as to form a photoresist film on a substrate orwafer. One or more of the compositions can be formulated to besubstantially free from cage groups, adamantyl groups, lactone groups,and/or ligand groups. Sensitizers can be included in compositions forincreasing a sensitivity of the resist material to the lithographicradiation. Selections for polymer components, resin components, acidgenerators, solvents, and solubility-shifting components can be selectedfrom conventionally available chemistries based on a given design orpatterning specifications to formulate a photoresist that is negativetone developer compatible without providing substantial or effectiveetch resistance. For example, an etch resistance that is less than orabout equal to an etch resistance of a particular underlying layer to beetched would be ineffective. Conventionally, photoresist films providean etch resistance many times greater than a given target layer to beetched.

Photoresist compositions as disclosed herein can be beneficial for usein photolithography applications. For example, compositions herein canbe used for patterning applications. One example method of making apattern includes exposing a photoresist composition layer (a photoresistfilm) with a pattern of actinic radiation (typically of one or morepredetermined wavelengths of light) and developing the pattern bytreatment with an organic solvent developer (negative tone developer) toform a negative tone relief image, that is, a topographically patternedlayer of photoresist. Note, however, that this topographically patternedlayer of photoresist (immediately after this development step) is freefrom components designed to provide or promote etch resistance. Theadvantage of a photoresist lacking functional groups that provide etchresistance is that a patterned photoresist has very smooth lines. Onedrawback of functional groups that provide etch resistance is that theseadditives are relatively bulky and increase surface roughness of adeveloped photoresist. The result of patterning with photoresistsdisclosed herein is creating a relief pattern resist layer with very lowline edge roughness or line width roughness. This particular reliefpattern, however, cannot be transferred into an underlying layer viaconventional etch techniques because the photoresist layer provideslittle or no etch resistance.

Other techniques herein include methods of using any of theabove-described compositions, including use in patterning methods. Thesemethods generally include forming a film from such compositions, andthen lithographically patterning the film to create a relief ortopographic pattern. For example, a pattern forming method can includeforming a photoresist film by depositing a photoresist composition on asubstrate. The photoresist composition can include any of theabove-described compositions. For example, this can include a positivetone photoresist component that is soluble to an organic solvent, aradiation-sensitive acid generator that generates photo acid in responseto exposure to a predetermined wavelength of light, and asolubility-shifting component that, in response to the presence of photoacid, causes the positive tone photoresist component to become insolubleto an organic solvent developer. This photoresist film is exposed tolithographic radiation, such as by using a scanner or stepper tool. Thenthe photoresist film is developed using negative tone development suchthat unexposed portions of the photoresist film are dissolved by anorganic solvent developer (or other negative tone developer) resultingin a topographic patterned photoresist film, wherein the topographicpatterned photoresist film has an Ohnishi parameter value greater than b3.0.

In other embodiments, an amount of functional groups included in thephotoresist composition or resist film that increase etch resistance toa wet etch or dry etch process, ranges from 0.0% to 15% by weight basedon a total weight of solid content in the photoresist composition. Inother embodiments, the photoresist composition, when deposited on asubstrate as a photoresist film, provides an etch resistivity such thata given plasma-based etching process etches the photoresist film at agreater etch rate than the given plasma-based etching process etches amaterial selected from the group consisting of silicon dioxide, silicon,polycrystalline silicon, silicon nitride, tetraethyl orthosilicate,amorphous carbon, and silicon oxynitride. In other words, thephotoresist film has or provides an etch resistance less than that of anunderlying target layer or memorization layer (sacrificial transferlayer).

Other embodiments include creating or increasing etch resistivity of thetopographic patterned photoresist film after developing the photoresistfilm using one or more post-processing techniques. One advantage ofdeveloping latent patterns using compositions herein is substantiallyreduced surface roughness or line edge/line width roughness, primarilybecause of a lack of resist-promoting additives. Such compositionsherein, however, run counter to conventional practices because reliefpattern films herein would be ineffective functioning as an etch mask.

Techniques herein also include post-processing techniques(post-development techniques) for transferring patterns into one or moreunderlying layers. One type of post-processing technique involvesphysically or chemically strengthening the topographically patternedphotoresist layer prior to etch transfer. Another type ofpost-processing technique involves multiple different methods forreversing the topographically patterned photoresist layer prior to etchtransfer.

One technique for strengthening a patterned photoresist layer includesan exposure to ballistic electrons. Such a treatment can occur in aplasma processing chamber that includes an upper electrode. A substratehaving a film of photoresist as disclosed herein is mounted on asubstrate holder of a plasma processing chamber such as acapacitively-coupled plasma processing chamber. In this chamber theupper electrode has a silicon or silicon oxide coating or plate. Aplasma is generated in the processing chamber using radiofrequency powertransmitted to either the upper electrode or the lower electrode.Negative voltage direct current is then coupled to the upper electrode.This negative charge in the upper electrode attracts positively chargedions which strike the upper electrode ejecting silicon and electrons.Due to the negative voltage present, the electrons are acceleratedtowards the substrate. These electrons striking the photoresist layercause one or more polymers within the photoresist layer to becomehardened or more etch resistant.

A thin layer of silicon can be simultaneously and conformally depositedon the photoresist layer via sputter deposition. This ballisticelectrons treatment can be labeled as direct current superposition.After the photoresist layer has become sufficiently etch resistant byexposure to the ballistic electrons, a topographically patternedphotoresist layer can then be directly transferred into an underlyinglayer via one or more etch processes. Such etch processes can includewet etch processes (hydrofluoric acid), or plasma-based dry etchprocesses using one or more mixtures of gases that can chemically and/orphysically react with an underlying layer.

FIGS. 1A-1E show a schematic cross-section substrate segment of aphotoresist strengthening process using ballistic electrons. In FIG. 1Aa photoresist layer 110 or film is being exposed to a pattern ofradiation (actinic radiation 175), such as by using a photomask 172.This layer or film is compatible with negative tone development.Photoresist layer 110 is positioned on target layer 107. Accordingly,developing a latent pattern in this photoresist layer results in removalof areas that were not exposed to radiation, as shown in FIG. 1B. Thus,photoresist layer 110 becomes relief pattern 111. FIG. 1C shows asubstrate being exposed to ballistic electrons via a plasma processingchamber. Negative polarity direct current power is coupled to an upperelectrode 163 of a plasma processing system. A flux of electrons 161 isaccelerated from the upper electrode 163 with sufficient energy to passthrough plasma 165 and strike the substrate such that an exposed surfaceof the relief pattern 111 changes in physical properties includingbecoming unresponsive to solubility shifts. In FIG. 1D an etch operationhas been executed that transferred a pattern defined by the reliefpattern 111 into a target layer 107 or other underlying layer. Thephotoresist material can then be completely removed resulting in atarget layer on the substrate having been patterned as shown in FIG. 1D,resulting in a patterned underlying layer in FIG. 1E.

Another technique for increasing etch resistivity of a topographicallypatterned photoresist layer includes an atomic layer deposition processfollowed by an etch process. FIGS. 2A-2F illustrate this processgenerally. Note that in the Figures, FIGS. 2A and 2B are similar toFIGS. 1A and 1B. For example, one or more material layers areconformally deposited on the patterned photoresist layer via atomiclayer deposition as shown by film 131 in FIG. 2C. Atomic layerdeposition is a known deposition technique for depositing highlyconformal layers, typically one layer of atoms or molecules at a time.With such a conformal layer on the patterned photoresist a conventionaletch process (typically anisotropic) is executed. In areas where theconformal layer covers only an underlying layer, the etch process etchesthrough the conformal layer and continues into the underlying layer. Inareas where there is photoresist material, the conformal layer interactswith the photoresist material and the etch mechanism (e.g. tanglingligand groups) essentially hardens the photoresist material and provideetch resistance (FIG. 2D), thereby enabling pattern transfer (FIG. 2E)resulting in a patterned target layer shown in FIG. 2F.

Another embodiment herein includes a pattern reversal technique (FIGS.3A-3E). This reversal technique can include depositing a conformalprotection layer on the substrate such that this conformal protectionlayer covers exposed surfaces of the topographic patterned photoresistfilm as well as exposed surfaces of an underlying target layer. Notethat FIGS. 3A and 3B are similar to FIGS. 1A and 1B. An exampleschematic depiction of this is shown in FIG. 3C. Next, achemical-mechanical polishing (CMP) step is executed. This CMP stepremoves the topographically patterned photoresist film but leaves theconformal protection layer on the target layer as shown in FIG. 3D.Thus, beneficial selections for the conformal protection layer includematerials that provide a good CMP stop layer and that are etch resistiverelative to the underlying layer. By way of a non-limiting example,silicon nitride can be selected for use in the conformal protectionlayer. In this step, an abrasive pad can physically remove uprightstructures containing both photoresist and the conformal protectionlayer, while leaving the conformal protection layer on surfaces of theunderlying substrate. With the photoresist layer essentially removed, anetch operation can transfer a pattern defined by the conformalprotection layer into the underlying layer (FIG. 3E).

Another embodiment herein includes a pattern reversal technique. Anexample sequence for this technique is shown in FIGS. 4A-4F. Note thatFIGS. 4A and 4B are similar to FIGS. 1A and 1B. Pattern reversal caninclude depositing a planarization layer 117 on a substrate such thatthe planarization layer fills openings defined by the topographicallypatterned photoresist film and at least covers exposed surfaces of anunderlying target layer (FIG. 4C). Note that completely filling definedopenings is not necessary, though in practice defined openings willusually be filled, with the photoresist film also being covered. Thiscan be a typical deposition result when using a spin-on depositiontechnique for planarization layer material. Spin-on deposition wouldtypically fill openings and cover the photoresist layer. Thisplanarization layer can be an oxide layer, for example. Thetopographically patterned photoresist film is then removed while leavingthe planarization layer (FIG. 4D). Such removal can be executed via anetch process. For example, a given chemistry is selected such as forplasma-based dry etching, and then the substrate is etched apredetermined distance or until the photoresist layer is uncovered. Uponuncovering the photoresist layer, this photoresist layer may beimmediately etched away. With the photoresist layer removed, a patterndefined by the planarization layer is then transferred into anunderlying layer via an etch process (FIGS. 4E-4F). This etch processcould be different or identical chemistry to the etch process used touncover the photoresist layer.

In another embodiment, a pattern reversal technique can be used based onacid diffusion as illustrated in FIGS. 5A-5H and 5J. Note that FIGS. 5Aand 5B are similar to FIGS. 1A and 1B. The planarization layer 117 isdeposited on the substrate such that the planarization layer fillsopenings defined by the relief pattern 111 and covers the relief pattern111. In this embodiment, a material selected as the planarization layeris a material capable of having a solubility shift. Example material isanother photoresist material. This photoresist material can have etchresistive properties. FIG. 5C shows an example result of an overcoat ofplanarization layer material. Next, an acid 119 can be deposited on theplanarization layer as shown in FIG. 5D. The acid 119 is then diffusedinto an upper portion of the planarization layer 117. This upper portionextends from a top surface of the planarization layer to a top surfaceof the relief pattern 111. The acid diffusing into the planarizationlayer causes the upper portion of the planarization layer to becomesoluble to a predetermined solvent. FIG. 5E shows an upper portion ofthe planarization layer having become soluble to the predeterminedsolvent. The upper portion of the planarization layer is then removedusing the predetermined solvent, with the result illustrated in FIG. 5F.Note in this illustration that the relief pattern 111 has beenuncovered. The relief pattern 111 is then removed while leaving theplanarization layer 117 (FIG. 5G). Removal can be accomplished using anetch process. The topographically patterned photoresist film does notinclude functional groups that provide etch resistance, whereas theplanarization layer (which could also be a photoresist) can be etchresistive. A pattern defined by the planarization layer can betransferred into the underlying layer via an etch process (FIGS. 5H and5J).

Another technique for using a non-resistive photoresist layer is toreverse a patterned photoresist using a self-aligned double patterningtechnique. An example process sequence in shown in FIGS. 6A-6G. Notethat FIGS. 6A and 6B are similar to FIGS. 1A and 1B. Self-aligned doublepatterning in general is known. In this technique a conformal film 144or semi-conformal film is deposited on the relief pattern 111 and coversthe relief pattern 111 (FIG. 6C). An anisotropic etch process isexecuted so as to remove the conformal film from horizontal surfaces onthe substrate leaving sidewall spacers 145 on sidewalls of the reliefpattern 111 (FIG. 6D). With sidewall spacers 145 formed, the initialpattern has essentially been multiplied in density. If any of thetopographically patterned photoresist remains after the etch process,the remainder can be removed using an ashing process or different etchprocess (FIG. 6E). The sidewall spacers remain on the target layer 107can then be used as an etch mask to transfer a pattern into target layer107 via an etch process (FIG. 6F), and then any remaining sidewallspacer material can be removed from the substrate (FIG. 6G).

Compositions and methods of use as disclosed herein can also help enableEUV (extreme ultraviolet) photolithography. In some EUV applications,conventional photoresist material does not perform as intended. Whenexposed to EUV radiation, such conventional resist materials areincapable of withstanding this radiation and either largely or entirelydisappear. As a consequence, there is insufficient photoresist to beable to transfer a pattern and so having etch resistance within thephotoresist film becomes inconsequential has discovered herein. Withcompositions as disclosed herein, removing functional groups (omittinginclusion of functional groups) that promote etch resistance, otherfunctional groups can be added that can withstand EUV radiation.

Compositions and methods herein can also be used to remove defectsassociated with EUV exposure. For example, a non-resistive photoresistfilm can be exposed using an EUV photomask and then developed using anegative tone developer. This image can then be reversed using one ormore techniques as previously described, and then a second layer ofnon-resistive photoresist film can be used with a same EUV photomask.With defects rarely if ever falling in a same place twice, by exposingthe same EUV reticle again, defects can be eliminated.

Another challenge discovered with conventional photolithography is thatresist films used for both conventional and EUV lithography arepractically too thin to enable proper transfer. A trend with resistformulations is adding more cage groups and other functional groups thatpromote etch resistance but that result in greater line edge roughness.Additives that increase resistivity are not only bulky but also increasecost. Thus, compositions and methods herein can provide patternedresists that are both smoother and more cost-effective than conventionalphotoresists.

In the preceding description, specific details have been set forth, suchas a particular geometry of a processing system and descriptions ofvarious components and processes used therein. It should be understood,however, that techniques herein may be practiced in other embodimentsthat depart from these specific details, and that such details are forpurposes of explanation and not limitation. Embodiments disclosed hereinhave been described with reference to the accompanying drawings.Similarly, for purposes of explanation, specific numbers, materials, andconfigurations have been set forth in order to provide a thoroughunderstanding. Nevertheless, embodiments may be practiced without suchspecific details. Components having substantially the same functionalconstructions are denoted by like reference characters, and thus anyredundant descriptions may be omitted.

Various techniques have been described as multiple discrete operationsto assist in understanding the various embodiments. The order ofdescription should not be construed as to imply that these operationsare necessarily order dependent. Indeed, these operations need not beperformed in the order of presentation. Operations described may beperformed in a different order than the described embodiment. Variousadditional operations may be performed and/or described operations maybe omitted in additional embodiments.

“Substrate” or “target substrate” as used herein generically refers toan object being processed in accordance with the invention. Thesubstrate may include any material portion or structure of a device,particularly a semiconductor or other electronics device, and may, forexample, be a base substrate structure, such as a semiconductor wafer,reticle, or a layer on or overlying a base substrate structure such as athin film. Thus, substrate is not limited to any particular basestructure, underlying layer or overlying layer, patterned orun-patterned, but rather, is contemplated to include any such layer orbase structure, and any combination of layers and/or base structures.The description may reference particular types of substrates, but thisis for illustrative purposes only.

Those skilled in the art will also understand that there can be manyvariations made to the operations of the techniques explained abovewhile still achieving the same objectives of the invention. Suchvariations are intended to be covered by the scope of this disclosure.As such, the foregoing descriptions of embodiments of the invention arenot intended to be limiting. Rather, any limitations to embodiments ofthe invention are presented in the following claims.

1. A pattern forming method, the method comprising: forming a photoresist film by depositing a photoresist composition on a substrate, the photoresist composition including a positive tone photoresist component that is soluble to an organic solvent, a radiation-sensitive acid generator that generates photo acid in response to exposure to a predetermined wavelength of light, and a solubility-shifting component that, in response to the presence of photo acid, causes the positive tone photoresist component to become insoluble to an organic solvent developer; exposing the photoresist film to lithographic radiation; and developing the photoresist film using negative tone development such that unexposed portions of the photoresist film are dissolved by the organic solvent developer resulting in a topographic patterned photoresist film, wherein the topographic patterned photoresist film has an Ohnishi parameter value greater than 3.0.
 2. The method of claim 1, further comprising: depositing a planarization layer on the substrate such that the planarization layer fills openings defined by the topographic patterned photoresist film and covers exposed surfaces of an underlying layer; removing the topographic patterned photoresist film while leaving the planarization layer; and transferring a pattern defined by the planarization layer into the underlying layer via an etch process.
 3. The method of claim 2, wherein removing the topographic patterned photoresist film includes executing an etch process, the planarization layer being resistant to the etch process.
 4. The method of claim 2, further comprising: depositing a planarization layer on the substrate such that the planarization layer fills openings defined by the topographic patterned photoresist film and covers the topographic patterned photoresist film; diffusing an acid into an upper portion of the planarization layer from a top surface of the planarization layer to a top surface of the topographic patterned photoresist film, the acid causing the upper portion of the planarization layer to become soluble to a predetermined solvent; removing the upper portion of the planarization layer using the predetermined solvent; removing the topographic patterned photoresist film while leaving the planarization layer; and transferring a pattern defined by the planarization layer into the underlying layer via an etch process.
 5. The method of claim 1, further comprising: depositing a semi-conformal or conformal film on the topographic patterned photoresist film that covers the topographic patterned photoresist film; executing an anisotropic etch process that removes the semi-conformal film from horizontal surfaces leaving sidewall spacers; and transferring a pattern defined by the sidewall spacers into an underlying layer via an etch process.
 6. A pattern forming method, the method comprising: forming a photoresist film by depositing a photoresist composition on a target layer of a substrate, the photoresist composition including a positive tone photoresist component that is soluble to an organic solvent, a radiation-sensitive acid generator that generates photo acid in response to exposure to a predetermined wavelength of light, and a solubility-shifting component that, in response to the presence of photo acid, causes the positive tone photoresist component to become insoluble to an organic solvent developer; exposing the photoresist film to lithographic radiation; and developing the photoresist film using negative tone development such that unexposed portions of the photoresist film are dissolved by the organic solvent developer resulting in a topographic patterned photoresist film, wherein the topographic patterned photoresist film has an etch resistance less than the target layer.
 7. The method of claim 6, further comprising: increasing etch resistivity of the topographic patterned photoresist film after developing the photoresist film.
 8. The method of claim 7, wherein increasing etch resistivity includes exposing the topographic patterned photoresist film to a flux of electrons in a plasma chamber by applying negative voltage direct current to an upper electrode.
 9. The method of claim 7, wherein increasing etch resistivity includes depositing a conformal protection layer via atomic layer deposition.
 10. The method of claim 6, further comprising: depositing a conformal protection layer on the substrate such that the conformal protection layer covers exposed surfaces of the topographic patterned photoresist film and exposed surfaces of an underlying layer; executing a chemical-mechanical polishing step that removes the topographic patterned photoresist film but that leaves the conformal protection layer on the underlying layer; and transferring a pattern defined by the conformal protection layer into the underlying layer via an etch process.
 11. A method of patterning a substrate, the method comprising: depositing a radiation-sensitive material on a substrate, the radiation-sensitive material being soluble to negative tone developer, the radiation-sensitive material having a de-protection group and a photo acid generator; exposing the radiation-sensitive material to a photolithographic pattern of radiation such that portions of the radiation-sensitive material being exposed to the photolithographic pattern of radiation become deprotected and soluble to a positive tone developer, the unexposed portions of the photolithographic pattern of radiation remaining soluble to a negative tone developer, and wherein the radiation sensitive material is substantially free of adamantyl groups and cage groups that provide etch resistance to an etching process; and developing the radiation-sensitive material using negative tone developer such that the radiation-sensitive material defines a patterned layer with portions of an underlying layer being uncovered. 